This invention relates to a method of preparing polyestercarbonates. More particularly the method relates to a method of preparing polyestercarbonates in which diacids rather than diesters are employed as starting materials and said diacids are incorporated into the polyestercarbonate backbone with a high level of efficiency.
Polyestercarbonates based on aliphatic diacids and aromatic bisphenols are known, commercially useful materials which are currently prepared under interfacial polymerization conditions comprising reaction of a mixture of a bisphenol such as bisphenol A (BPA) together with a dicarboxylic acid such as dodecandioic acid with phosgene in the presence of a solvent and an aqueous solution of an acid acceptor such as sodium hydroxide. xe2x80x9cSPxe2x80x9d polycarbonate which typifies such polyestercarbonates is a copolymer of BPA (xcx9c92 mole %) and dodecanedioic acid (DDDA) (xcx9c8 mole %) and is available from GE Plastics, Mt Vernon, Ind. Because the xe2x80x9cSPxe2x80x9d polycarbonate is prepared in the presence of a solvent, methylene chloride, the manufacture of xe2x80x9cSPxe2x80x9d polycarbonate currently requires a solvent removal. Solvent removal is typically carried out by introducing steam into a solution of the product polyestercarbonate, a process which can result in fusion of the isolated powder resin owing to the presence of solvent and the inherently lower glass transition temperatures of polyestercarbonates incorporating comonomer such as DDDA relative to the corresponding homopolycarbonates. Therefore only high molecular weight material can be manufactured this way.
An alternative route to polyestercarbonates using a melt process would be highly desirable to circumvent problems attending solvent removal and allow the manufacture of lower molecular weight polyestercarbonates having lower melt viscosities. However, utilizing the traditional melt polycarbonate approach utilizing diphenyl carbonate (DPC) as the carbonate source requires long reaction times and high temperatures to achieve high molecular weight. As an added drawback, less than 100% of the expensive DDDA is incorporated by this method. An alternate approach which circumvents this reduced reactivity of DDDA uses the diphenyl ester of DDDA in the melt polymerization. This approach, however, requires preparation of the diphenyl ester of the diacid and further escalates both the cost and complexity of the process. Thus, there exists a need for a new method which allows the efficient incorporation of diacid comonomers directly into polyestercarbonates without recourse to interfacial polymerization techniques and which demonstrate a higher level of efficiency than is observed using known melt polymerization techniques.
The present invention provides a method for the preparation of polyestercarbonates, said method comprising preparing a mixture comprising at least one activated diaryl carbonate, at least one dihydroxy aromatic compound, at least one diacid, at least one melt polymerization catalyst and optionally one or more co-catalysts, and heating under melt polymerization conditions to afford a product polyestercarbonate.
The method further relates to the preparation of polycarbonate esters having a high level of polymer endcapping.
The present invention may be understood more readily by reference to the following detailed description of preferred embodiments of the invention and the examples included therein. In the following specification and the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings:
The singular forms xe2x80x9caxe2x80x9d, xe2x80x9canxe2x80x9d and xe2x80x9cthexe2x80x9d include plural referents unless the context clearly dictates otherwise.
xe2x80x9cOptionalxe2x80x9d or xe2x80x9coptionallyxe2x80x9d means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
As used herein, the term xe2x80x9cmelt polycarbonatexe2x80x9d refers to a polycarbonate made by the transesterification of a diaryl carbonate with a dihydroxy aromatic compound.
xe2x80x9cBPAxe2x80x9d is herein defined as bisphenol A or 2,2-bis(4-hydroxyphenyl)propane.
xe2x80x9cCatalyst systemxe2x80x9d as used herein refers to the catalyst or catalysts that catalyze the transesterification of the bisphenol with the diaryl carbonate in the melt process.
xe2x80x9cCatalytically effective amountxe2x80x9d refers to the amount of the catalyst at which catalytic performance is exhibited.
As used herein the term xe2x80x9caliphatic radicalxe2x80x9d refers to a radical having a valence of at least one comprising a linear or branched array of atoms which is not cyclic. The array may include heteroatoms such as nitrogen, sulfur and oxygen or may be composed exclusively of carbon and hydrogen. Examples of aliphatic radicals include methyl, methylene, ethyl, ethylene, hexyl, hexamethylene and the like.
As used herein the term xe2x80x9caromatic radicalxe2x80x9d refers to a radical having a valence of at least one comprising at least one aromatic group. Examples of aromatic radicals include phenyl, pyridyl, furanyl, thienyl, naphthyl, phenylene, and biphenyl. The term includes groups containing both aromatic and aliphatic components, for example a benzyl group.
As used herein the term xe2x80x9ccycloaliphatic radicalxe2x80x9d refers to a radical having a valance of at least one comprising an array of atoms which is cyclic but which is not aromatic. The array may include heteroatoms such as nitrogen, sulfur and oxygen or may be composed exclusively of carbon and hydrogen. Examples of cycloaliphatic radicals include cyclcopropyl, cyclopentyl cyclohexyl, tetrahydrofuranyl and the like.
As used herein the abbreviation xe2x80x9cBMSCxe2x80x9d stands for the activated diaryl carbonate bis(methyl salicyl) carbonate (CAS No. 82091-12-1).
The present invention provides a method for preparing polyestercarbonates by reacting under melt polymerization conditions at least one activated diaryl carbonate with at least one dihydroxy aromatic compound and at least one diacid in the presence of a catalytically effective amount of at least one melt polymerization catalyst and optionally one or more co-catalyst.
The activated diaryl carbonate used according to the method of the present invention is xe2x80x9cactivatedxe2x80x9d in the sense that it undergoes transesterification reaction under melt polymerization conditions with a dihydroxy aromatic compound at a rate faster than the rate of the corresponding reaction of diphenyl carbonate. Activated diaryl carbonates thus encompass diaryl carbonates substituted with one or more electronegative substitutents such as halogen, cyano, perhaloalky, nitro, acyl and the like. Examples of activated diaryl carbonates for use according to the method of the present invention include bis(2-acetylphenyl) carbonate, bis(4-acetylphenyl) carbonate, bis(2-pivaloylphenyl) carbonate, bis(4-pivaloylphenyl) carbonate, bis(2-cyanophenyl) carbonate, bis(4-cyanophenyl) carbonate, bis(2-chlorophenyl) carbonate, bis(4-chlorophenyl) carbonate, bis(2, 4-dichlorophenyl) carbonate, bis(2, 4, 6-trichlorophenyl) carbonate, bis(2-nitrophenyl) carbonate, bis(4-nitrophenyl) carbonate, bis(2-fluorophenyl) carbonate, bis(2, 4-difluorophenyl) carbonate, bis(2, 4, 6-trifluorophenyl) carbonate, bis(2-trifluoromethylphenyl) carbonate, bis(4-trifluoromethylphenyl) carbonate, bis(2-chloro-4-trifluoromethylphenyl) carbonate, and the like.
In one embodiment the activated diaryl carbonate used according to the method of the present invention has structure I 
wherein R1 and R2 are independently C1-C20 alkyl radicals, C4-C20 cycloalkyl radicals or C4-C20 aromatic radicals, R3 and R4 are independently at each occurrence a halogen atom, cyano group, nitro group, C1-C20 alkyl radical, C4-C20 cycloalkyl radical, C4-C20 aromatic radical, C1-C20 alkoxy radical, C4-C20 cycloalkoxy radical, C4-C20 aryloxy radical, C1-C20 alkylthio radical, C4-C20 cycloalkylthio radical, C4-C20 arylthio radical, C1-C20 alkylsulfinyl radical,C4-C20 cycloalkylsulfinyl radical, C4-C20 arylsulfinyl radical, C1-C20 alkylsulfonyl radical, C4-C20 cycloalkylsulfonyl radical, C4-C20 arylsulfonyl radical, C1-C20 alkoxycarbonyl radical, C4-C20 cycloalkoxycarbonyl radical, C4-C20 aryloxycarbonyl radical, C2-C60 alkylamino radical, C6-C60 cycloalkylamino radical, C5-C60 arylamino radical, C1-C40 alkylaminocarbonyl radical, C4-C40 cycloalkylaminocarbonyl radical, C4-C40 arylaminocarbonyl radical, and C1-C20 arylamino radical; and b and c are independently integers 0-4.
Examples of activated diaryl carbonates having structure I include bis(methyl salicyl) carbonate (BMSC), bis(ethyl salicyl) carbonate, bis(propyl salicyl) carbonate, bis(butyl salicyl) carbonate, bis(benzyl salicyl) carbonate, and bis(methyl 4-chlorosalicyl) carbonate. Typically BMSC is preferred.
The dihydroxy aromatic compound used according to the method of the present invention is typically selected from the group consisting of bisphenols having structure II, 
wherein R5-R12 are independently a hydrogen atom, halogen atom, nitro group, cyano group, C1-C20 alkyl radical C4-C20 cycloalkyl radical, or C6-C20 aryl radical; W is a bond, an oxygen atom, a sulfur atom, a SO2 group, a C6-C20 aromatic radical, a C6-C20 cycloaliphatic radical or the group 
wherein R13 and R14 are independently a hydrogen atom, C1-C20 alkyl radical, C4-C20 cycloalkyl radical, or C4-C20 aryl radical; or R13 and R14 together form a C4-C20 cycloaliphatic ring which is optionally substituted by one or more C1-C20 alkyl, C6-C20 aryl, C5-C2, aralkyl, C5-C20 cycloalkyl groups or a combination thereof; dihydroxy benzenes having structure III 
wherein R15 is independently at each occurrence a halogen atom, nitro group, cyano group, C1-C20 alkyl radical, C4-C20 cycloalkyl radical C4-C20 aryl radical; and d is an integer from 0 to 4;
and dihydroxy naphthalenes having structures IV and V 
wherein R16, R17, R18 and R19 are independently at each occurrence a halogen atom, nitro group, cyano group, C1-C20 alkyl radical, C4-C20 cycloalkyl radical C4-C20 aryl radical; e and f are integers of from 0 to 3, g is an integer from 0 to 4, and h is an integer from 0 to 2.
Examples of bisphenols having structure II include 2,2-bis(4-hydroxyphenyl)propane (bisphenol A); 2,2-bis(3-methyl-4-hydroxyphenyl)propane; 1,1-bis(4-hydroxyphenyl)cyclohexane; 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane; 1,3-bis(2-(4-hydroxyphenyl)-2-propyl)benzene; 1,4-bis(2-(4-hydroxyphenyl)-2-propyl)benzene; and 1,4-bis(2-(4-hydroxy-3-methylphenyl)-2-propyl)benzene.
Examples of dihydroxy benzenes having structure III include hydroquinone, resorcinol, methylhydroquinone, phenylhydroquinone, 4-phenylresorcinol; and 4-methylresorcinol.
Examples of dihydroxy naphthalenes having structure IV include 2,6-dihydroxy naphthalene; 2,6-dihydroxy-3-methyl naphthalene; 2,6-dihydroxy-3-phenyl naphthalene and of 2,8-dihydroxy naphthalene.
Examples of dihydroxy naphthalenes having structure V include 1,4-dihydroxy naphthalene; 1,4-dihydroxy-2-methyl naphthalene; 1,4-dihydroxy-2-phenyl naphthalene and 1,3-dihydroxy naphthalene.
The diacid may be an aromatic diacid such as 2,6-nathalene dicarboxylic acid, an aliphatic diacid such as succinic acid, or a cycloaliphatic di acid such as 1,7-cyclododecanedioic acid. Typically, the diacid employed is a diacid having structure VI
HO2Cxe2x80x94R20xe2x80x94COOHxe2x80x83xe2x80x83VI
wherein R20 is a C4-C30 aromatic radical, a C1-C40 aliphatic radical, or a C5-C30 cycloaliphatic radical.
In addition to those diacids referenced above, diacids having structure VI include terephthalic acid; isophthalic acid; 1,4-cyclohexanediacrboxylic acid; hexanedioic acid; octanedioic acid; decanedioic acid; dodecanedioic acid; tetradecanedioic acid; hexadecanedioic acid; octadecanedioic acid; cis 9-octenedioic acid; alpha-nonyldecanedioic acid; alpha-octylundecanedioic acid; and hydrogenated dimer acid. Dodecanedioic acid is frequently preferred.
The melt polymerization catalyst used according to the method of the present invention may be any of a wide variety of transesterifcation catalysts capable of effecting reaction between the activated diaryl carbonate, the aromatic dihydroxy compound and the diacid present in the reaction mixture. The melt polymerization catalyst may be a single compound or a mixture of compounds and may be employed in combination with one or more co-catalysts such as quaternary ammonium salts or quaternary phosphonium salts.
From the standpoint of both cost and efficiency it has been found that metal hydroxides such as alkali metal hydroxides and alkaline earth metal hydroxides are well adapted to serve as melt polymerization catalysts, although a variety of other catalysts are well suited to this task.
Examples of alkaline earth metal hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide, and mixtures thereof. Examples of alkaline earth metal hydroxides include calcium hydroxide, barium hydroxide, and mixtures thereof.
Other melt polymerization catalysts which may be used advantageously according to the method of the present invention include alkali metal salts of carboxylic acids, alkaline earth metal salts of a carboxylic acids, and mixtures thereof. Alkali metal salts of carboxylic acids include lithium acetate, sodium benzoate, and dipotassium dodecanedioate. Examples of alkaline earth metal salts of a carboxylic acids include calcium benzoate, calcium adipate, and barium acetate. The catalyst used according to the method of the present invention may the salt of a polycarboxyic acid such a tetrasodium ethylenediamine tetracarboxylate, or disodium magnesium ethylenediamine tetracarboxylate. Thus, salts of polycarboxylic acids comprising a variety of metal cations may be employed as the melt polymerization catalyst according to the method of the present invention, disodium magnesium ethylenediaminetetracarboxylate serving as an example of a salt of a polycarboxylic acid comprising both alkali metal and alkaline earth metal cations.
In one embodiment of the present invention the melt polymerization catalyst comprises the salt of a non-volatile acid. By xe2x80x9cnon-volatilexe2x80x9d it meant that the acid from which the catalyst is made has no appreciable vapor pressure under melt polymerization conditions. Examples of non-volatile acids include phosphorous acid, phosphoric acid, sulfuric acid, and metal xe2x80x9coxo acidsxe2x80x9d such as the oxo acids of germanium, antimony, niobium and the like. Salts of non-volatile acids useful as melt polymerization catalysts according to the method of the present invention include alkali metal salts of phosphites; alkaline earth metal salts of phosphites; alkali metal salts of phosphates; alkaline earth metal salts of phosphates, alkali metal salts of sulfates, alkaline earth metal salts of sulfates, alkali metal salts of metal oxo acids, and alkaline earth metal salts of metal oxo acids. Specific examples of salts of non-volatile acids include NaH2PO3, NaH2PO4, Na2H2PO3, KH2PO4, CsH2PO4, CsH2PO4, Cs2H2PO4, Na2SO4, NaHSO4, NaSbO3, LiSbO3, KSbO3, Mg(SbO3)2, Na2GeO3, K2GeO3, Li2GeO3, Mg GeO3, Mg2GeO4, and mixtures thereof.
Typically the melt polymerization catalyst is employed in an amount equivalent to between about 1.0xc3x9710xe2x88x928 and about 1xc3x9710xe2x88x923, preferably between about 1.0xc3x9710xe2x88x928 and about 1xc3x9710xe2x88x925 moles of melt polymerization catalyst per mole of dihydroxy aromatic compound.
As mentioned, the method of the present invention may be practiced using a co-catalyst. Typically, the co-catalyst is a quaternary ammonium salt or quaternary phosphonium salt and is used in an amount corresponding to about 10 to about 250 times the molar amount of melt polymerization catalyst used. The catalyst and co-catalyst, may be added to the reaction mixture either simultaneously, or the catalyst and co-catalyst may be added separately at different stages of the polymerization reaction.
In one embodiment the co-catalyst comprises at least one quaternary ammonium salt having structure VII 
wherein R21-R24 are independently a C1-C20 alkyl radical, C4-C20cycloalkyl radical or a C4-C20 aryl radical and Xxe2x88x92 is an organic or inorganic anion.
In structure VII, the anion Xxe2x88x92 is typically an anion selected from the group consisting of hydroxide, halide, carboxylate, phenoxide, sulfonate, sulfate, carbonate, and bicarbonate. Examples of quaternary ammonium salts having structure VII include tetramethylammonium hydroxide, tetrabutylammonium acetate and the like.
In an alternate embodiment of the present invention, a quaternary phosphonium co-catlayst is employed, said co-catalyst having structure VII 
wherein R25-R28 are independently a C1-C20 alkyl radical, C4-C20cycloalkyl radical or a C4-C20 aryl radical and Xxe2x88x92 is an organic or inorganic anion.
In structure VIII, the anion Xxe2x88x92 is typically an anion selected from the group consisting of hydroxide, halide, carboxylate, phenoxide, sulfonate, sulfate, carbonate, and bicarbonate. Examples of quaternary phosphonium salts having structure VIIl include tetramethylphsophonium hydroxide, tetrabutylphosphonium acetate, tetrabutylphosphonium hydrogen carbonate, and the like.
With respect to co-catalysts having structures VII and VII, where Xxe2x88x92 is a polyvalent anion such as carbonate or sulfate it is understood that the positive and negative charges in structures VII and VII are properly balanced. For example, where R25-R28 in structure VIII are each butyl groups and Xxe2x88x92 represents a carbonate anion, it is understood that Xxe2x88x92 represents xc2xd(CO3xe2x88x922).
Typically, the reactants are employed according to the method of the present invention such that the molar ratio of activated diaryl carbonate to the total moles of aromatic dihydroxy compound and diacid is in a range between about 1.01 and about 2, preferably between about 1.01 and about 1.5, and still more preferably between about 1.01 and about 1.2. For example, in an embodiment wherein 2 moles of bis(methyl salicyl) carbonate is polymerized reacted with 0.95 moles of bisphenol A and 0.05 moles of adipic acid, the molar ratio of activated diaryl carbonate to aromatic dihydroxy compound and diacid is 2 to 1. Typically, the amount of dicarboxylic acid employed is a range between about 0.01 about 0.10 moles of dicarboxylic acid per mole of aromatic dihydroxy compound employed.
The reaction conditions of the melt polymerization are not particularly limited and may be conducted under a wide range of operating conditions. Hence, the term xe2x80x9cmelt polymerization conditionsxe2x80x9d will be understood to mean those conditions necessary to effect reaction between the activated diaryl carbonate, the dihydroxy aromatic compound, and the diacid of the present invention to afford a polyestercarbonate having sufficiently high molecular weight to possess useful polymer properties. Typically, the product polyestercarbonate has useful polymer properties when it possesses a weight average molecular weight of about 18,000 daltons or greater. The reaction temperature is typically in the range from about 150xc2x0 C. to about 330xc2x0 C. and preferably from about 170xc2x0 C. to about 280xc2x0 C. The pressure may be at atmospheric pressure, supraatmospheric pressure, or a range of pressures from atmospheric pressure to about 15 torr in the initial stages of the reaction, and at a reduced pressure at later stages, for example in the range of about 0.01 to about 15 torr. The reaction time is generally about 0.1 hours to about 10 hours.
In one embodiment of the present invention, reactants bis(methyl salicyl) carbonate, bisphenol A and dicarboxylic acid having structure VI are heated under melt polymerization conditions for a period of between about 0.1 and about 10 hours to a temperature in a range between about 150xc2x0 C. and about 310xc2x0 C. at a pressure in a range between about atmospheric pressure and about 0.01 torr, in the presence of a melt polymerization catalyst, said melt polymerization catalyst being present in an amount corresponding to between about 1.0xc3x9710xe2x88x928 and about 1xc3x9710xe2x88x923 moles per mole of bisphenol A, and a co-catalyst, said co-catalyst being present in an amount corresponding to between about 10 times and about 250 times the number of moles of melt polymerization catalyst.
The method of the present invention may be practiced in either a continuous or batch mode and may be conducted in stages, for example an initial oligomerization stage followed by a separate stage in which the initially formed oligomers are converted to higher molecular weight product. The method of the present invention is not particularly limited with respect to the reaction equipment employed. Any reactor, batch or continuous, capable of melt mixing the polymerization mixture and removing volatile side products may be used. Because of their high efficiency continuous reactors are preferred.